Chen Taiyu, Wu Huan, Wu Jiemin, Fan Xiaolei, Li Xianghua, Lin Yongjun
National Key Laboratory of Crop Genetic Improvement, Huazhong Agriculture University, Wuhan, 430070, China.
College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Plant J. 2017 Apr;90(2):344-357. doi: 10.1111/tpj.13497. Epub 2017 Mar 20.
Plants always adjust the opening of stomatal pores to adapt to the environment, for example CO concentration ([CO ]), humidity and temperature. Low [CO ] will trigger the opening of stomatal pores to absorb extra CO . However, little is known about how CO supply affects the carbon fixation and opening of stomatal pores in rice. Here, a chloroplast-located gene coding for β-carbonic anhydrase (βCA) was found to be involved in carbon assimilation and the CO -mediated stomatal pore response in rice. OsβCA1 was constitutively expressed in all tissues and its transcripts were induced by high [CO ] in leaves. Both T-DNA mutant and RNA interference lines showed phenotypes of lower biomass and CA activities. Knockout of OsβCA1 obviously decreased photosynthetic capacity, as demonstrated by the increased CO compensation point and decreased light saturation point in the mutant, while knockout increased the opening ratio of stomatal pores and the rate of water loss. Moreover, the mutant showed a delayed response to low [CO ], and stomatal pores could not be closed to the same degree as those of wild type even though the stomatal pores could rapidly respond to high [CO ]. Genome-wide gene expression analysis via RNA sequencing demonstrated that the transcript abundance of genes related to Rubisco, photosystem compounds and the opening of stomatal pores was globally upregulated in the mutant. Taken together, the inadequate CO supply caused by the absence of OsβCA1 reduces photosynthetic efficiency, triggers the opening of stomatal pores and finally decreases their sensitivity to CO fluctuation.
植物总是会调节气孔的开度以适应环境，例如二氧化碳浓度（[CO₂]）、湿度和温度。低[CO₂]会促使气孔张开以吸收额外的二氧化碳。然而，关于二氧化碳供应如何影响水稻的碳固定和气孔开度，人们了解甚少。在这里，发现一个编码β-碳酸酐酶（βCA）的叶绿体定位基因参与了水稻的碳同化以及二氧化碳介导的气孔反应。OsβCA1在所有组织中组成型表达，其转录本在叶片中受高[CO₂]诱导。T-DNA突变体和RNA干扰株系均表现出生物量较低和CA活性较低的表型。敲除OsβCA1明显降低了光合能力，这在突变体中表现为二氧化碳补偿点升高和光饱和点降低，而敲除则增加了气孔的开放率和失水率。此外，突变体对低[CO₂]的反应延迟，即使气孔能够对高[CO₂]快速做出反应，其气孔也无法像野生型那样关闭到相同程度。通过RNA测序进行的全基因组基因表达分析表明，与Rubisco、光合系统复合物和气孔开度相关的基因转录丰度在突变体中整体上调。综上所述，OsβCA1缺失导致的二氧化碳供应不足降低了光合效率，触发了气孔的开放，最终降低了它们对二氧化碳波动的敏感性。
